Combine 2 tablespoons of olive oil with 3 cloves of minced garlic and mix well. Rub this mixture all over the lamb, then sprinkle with salt and pepper and place in a roasting pan.

Cook the lamb in a preheated 450° oven for 15 minutes, then reduce the heat to 350° and cook another 30 minutes. Check the internal temperature with a meat thermometer. It should read 130° for medium rare with a pink center. A reading of 150° will give you medium well with no pink meat. Remove the lamb from the oven and let sit for 15 minutes before carving into thick slices.

While the lamb rests, wash the spinach, and gently shake to remove excess water. Heat the remaining tablespoon of olive oil in a skillet over medium heat and sauté the onion 3–4 minutes until translucent. Add the remaining garlic and sauté for another minute. Place the spinach on top of the garlic and onion and put a lid over the skillet. Wait a minute or two, allowing the heat in the skillet to build up, then turn off the heat. The spinach will wilt nicely in 5–6 minutes. Mix the spinach, onion, and garlic, add salt and pepper to taste. Serve with carved lamb.